See instructions): The UCLA site has a 25-year history of outstanding performance as a clinical site of the MACS, maintaining current status information on over 88.5% of the 1637 participants. The empathetic, committed staff, most of whom have been with the study for more than 15 years (and some for 25 years), has been cited by participants as a key to their continued commitment to the UCLA MACS. State-of-the-art laboratory procedures have been implemented, and quality assurance procedures put in place. The Center has recruited an outstanding group of UCLA investigators to participate in the MACS, and to assume leadership roles in various scientific areas, taking leadership for 52 research publications since 2003 and contributing to 60 other MACS scientific papers. The objectives of the UCLA MACS Clinical Center are to: 1) Maintain the cohorts of men recruited in 1984-5 and the men more recently recruited in 2002-3 (primarily Hispanic-Americans and African-Americans); 2) Collect specific behavioral, clinical and psychosocial data, and laboratory specimens from the men; 3) Process laboratory specimens for the local and national specimen repositories of serum, plasma, and cells and to perform flow cytometry and serologic measurements on these samples from Los Angeles participants; 4) Maintain the local repository for use by local investigators; 5) Contribute to ongoing and future studies of cardiovascular complications, renal function, liver diseases, neurocognitive impairment, malignancies, aging, and genomic characteristics of MACS participants; 6) Contribute scientific leadership to the MACS through leadership of several MACS working groups (Core Laboratory, Malignancies/Pathology, Neuropsychology),organization of quality control procedures, leadership in key MACS papers and participation in others, and active participation in the bi-monthly conference calls and meetings of the MACS; 7) Recruit both experienced and new investigators who bring new scientific insights and skills that will enhance the quality and breadth of science in the MACS. RELEVANCE (Seeinstructions): The MACS incorporates a large database of information and biologic specimens collected every six months from 6,972 men followed since 1984-5 (primarily European-American) and 2002-3 (primarily Latino and Africa-American), and allows continuing observation of the 3243 survivors. Thus, the MACS provides an irreplaceable resourcefor continued study of the natural history of treated and untreated HIV infection and AIDS.